`getpeername()` is currently handled in ntdll. This merge request changes ntdll to forward `getpeername()` to wineserver. The implementation utilises new `peer_addr` and `peer_addr_len` fields in wineserver's `struct sock`.
This fixes multiple `todo_wine`s in `ws2_32/tests` and allows for more accurate peer names to be provided in case the address the socket is bound to on the Unix side does not match what `bind()` was called with on the Windows side.
*This merge request was originally intended to be included in !2786 (Add support for AF_UNIX sockets) but was split into its own merge request because this is not an insignificant change.*
-- v6: ws2_32/tests: Remove todo_wine from now-successful tests. server: Move getpeername() implementation from ntdll/unix.